As Ovid notes, the River Ister represents the boundary between one state of being and another. Particularly, the Ister here represents the painful transition from a known world into an unknown world. The river thus symbolizes suffering necessary for personal growth. Ovid’s feeling, midway across the river, that nothing exists at either shore implies that in the midst of suffering, one cannot always see the good that will come of it. Regardless, one must carry on until one emerge from the struggle.